1. Field of the Invention
This invention relates to conductor casings for oil and gas wells. More specifically, the invention is directed to a new and improved method and apparatus for deviating the conductor casing of the well as it is being driven into the substratum.
2. Description of the Prior Art
It is commonly known that oil and gas wells are commonly driven at varying slanted angles for a variety of reasons. For example, in order to increase the lateral reach of the well, or in order to tap a deposit in a number of locations, the conductors have been driven at a slant, with respect to vertical. In this procedure, the conductor casing itself generally remains uncurved, although the conductors have been pre-curved prior to their being driven into the substratum. One known method describes conductor driving by forcing them through an arcuately positioned set of guide members affixed to the superstructure of the platform. An example of a straight conductor driven at a slanted angle is shown in the U.S. Pat. No. 3,451,493. In offshore wells, the conductors are usually extended laterally beyond the perimeter of a platform at a substantial distance above the mud line thus producing an undesirable condition since it results in long spans of conductors which are unsupported or which require fabrication of conductor guides exteriorly of the main framework of the platform. This results in increased costs, time and unnecessary complications. An example of conductors which are slanted or curved during driving by forcing the conductors through a plurality of offset guide members is shown in U.S. Pat. No. 3,670,507. This type of apparatus and method is generally deficient because it precludes versatility in drilling due to the fixed construction of the guide means on the platform, and in any event the amount of curvature that can be obtained in the casing is predetermined by the preset guide means and may not be changed.
It thus becomes desirable to provide for a deviated conductor casing which is neither driven at an original slant or precurved through a series of arcuate guide members. In other words, it becomes desirable to drive the conductor pipe substantially vertically into the substratum and cause it to be deviated thereafter. In this regard, attention may be directed to U.S. Pat. No. 4,027,734 wherein there is shown a method for a deviated implacement of a conductor casing at a desired orientation in order to facilitate directional drilling of a well in the substratum at an offshore site. Here, there is suggested the method of diverting a conductor by means of welding a short section of pipe on the bottom of the conductor at a slight angle to the axis of the conductor. Before the straight conductor pipe is inserted in the vertically aligned guides, the short section is cut off and re-welded at a slight angle to the axis, thus creating a "dog-leg" for diverting the conductor in a predetermined direction as it is forced through the substratum soils. A problem, and limiting factor, arising with use of such a "dog-leg" deviated conductor is that the dog-leg itself can be deviated only a very minor distance off of the center line of the pipe due to the diameter of the preset guides. This offset distance may vary from 1/2 inch to the clearance allowed by the guide through which the offset section must pass. Such pre-set dog-leg section, commonly affixed such as by welding, is not only restricted as to the magnitude of the dog-leg to its inability to pass through a series of guide means, but also is substantially obstructed from utilization on a pre-curved conductor for the same reason.